Problem: The sum of $3$ consecutive odd numbers is $45$. What is the first number in this sequence?
Solution: Call the first number in the sequence $x$ The next odd number in the sequence is $x + 2$ The sum of the $3$ consecutive odd numbers is: $x+ (x + 2)+ (x + 4) = 45$ $3x + 6= 45$ $3x = 39$ $x = 13$ Thus, the first number is $13$.